How to create a ribbon and attach it to a balloon
a ribbon like that can be done extruding an open curve object (not pressing E, but using "extrude" slider in the curve panel). But you'll have to model its curves by hand, positioning the curve control points manually. 

Making it behave "automatically" like a real ribbon with spring effect, gravity, is more difficult though. I guess it would be more like a sort of cloth or soft body thing...

[edit]
First, experiment with something simple: another answer shows you how to create a simple bezier, and shape it as you wish adding control points, an that is right but slightly slow and tedious.

There is also a way to easily get a complete "twirled" ribbon, already shaped as a spiral, which you can perhaps more easily adapt to your taste, and get something like this:



This is what I suggest:


starting from a "vertical" (along z) plane, delete all vertices but 2 connected
in this way you should get a vertical segment of just 2 vertices, like this below

as suggested in the image, press the toolbar "screw" command: you immediately get what follows:

before confirming, adjust "steps" and "turns" (I suggest 3 steps, and a few turns, will explain later why)
then, you only need to keep one of the two the "edge loops" of the shape created by the screw command, like below (ctrl-right click on an edge to select it, or select 2 connected vertices on it and then CTRL-E => "edge loops"):

so, press "x" and delete those vertices (ot use CTRL-I to invert the selection, and delete the others, you get the same result for this purpose): you will get something like

now, convert the shape (objlect mode) to curve, with ALT-C:

this is now a curve but I know it doesn't seem a ribbon, now, since "screw" command had only 3 "steps" per "turn". But you can now apply a "subsurf" (subdivision surface) modifier to smooth it and you can change several levels, in a non-distructive way (you can change idea, try several versions):
 

then, since is a curve you can give "depth" using the extrude slider as said starting this post (I prefer "extrude" and not "bevel"). 
Just smooth the shading, and see what nice ribbon you have now!

Plus, since you chose only 3 "steps" per turn, you have fewer control points to change its shape, meaning: it's easier to pose, and animate! (this is why I suggested 3 steps, and several turns) 




But if you need more points, you can always select 2 of them and "subdivide", and get more fancy ribbon shapes!




Happy ribboning!